The landing phase is a critical phase of the flight of an aircraft since it is during this phase that incidents mostly occur. To ease the task of pilots, numerous automatic landing systems have been proposed. Known in particular is the instrument landing system or ILS fitted to large-capacity airliners and whose ground infrastructures are present in international airports. The MLS microwave landing system is also available in certain European airports. These systems use radio or microwave signals to guide the aircraft in its approach phase both laterally with respect to the axis of the runway and vertically with respect to the approach plane (glide path). However, they exhibit the drawback of not being available in all airports because in particular of their high costs and of exhibiting heavy constraints of use. Furthermore, the ground infrastructures exhibit a breakdown probability of the order of 10−3/hour. Aircraft may therefore not be certain of being able to perform a landing in automatic mode. Automatic landing systems, dubbed GLS (Ground based augmented system Landing System) or SLS (Satellite-based Landing System) which use satellite positioning, have appeared more recently. As current satellite positioning systems do not make it possible to obtain the precision required to perform a landing, they must be augmented with ground reference stations such as those of the WAAS (Wide Area Augmentation System) or EGNOS (European Geostationary Navigation Overlay Service) network. These systems are still not very widespread and exhibit a relatively low availability rate (of the order of 99.5%) which, once again, does not make it possible to permanently guarantee landing in automatic mode.
Because of the spatial and temporal unavailability of such ground infrastructures, interest has turned to autonomous landing systems, using video images of the ground, captured by an onboard camera.
These autonomous systems generally use the video images captured by the onboard camera and information relating to the runway to estimate the attitude and the position of the aircraft with respect to the runway. The aircraft guidance orders are thereafter computed on the basis of the position and attitude thus determined. However, this estimation is a complex operation, which generally requires the availability of an onboard digital model of the topography of the airport or at the very least of geometric and topographic information relating to the landing runway. Furthermore, when the database containing the digital model is unavailable or in case of emergency landing on an arbitrary field, the aforementioned autonomous systems are inoperative.
Application FR-A-2835314 filed by the present applicant proposes a landing aid system that does not make it necessary to know the characteristics of the landing runway. However, this system operates only when the aircraft is a few meters from the ground, according to a principle much like a driving aid in the road traffic context. In particular it does not make it possible to guide the aircraft throughout the final approach, that is to say during the last ten kilometers or so.
An object of the present disclosure is a system for automatic landing of an aircraft which is particularly robust, can operate in total or partial absence of information about the landing runway, and guide an aircraft in an autonomous manner throughout the final approach.